Optical modulators

Abstract

An object of the present invention is, in an optical modulator, to increase the production yield by enhancing the patterning accuracy of the electrodes, as well as to reduce the electrode loss by increasing the thickness of the electrodes. An optical modulator has a substrate 5 made of an electro-optical material; a modulation electrode 2 A, 3 A, 2 B provided on the substrate 5 ; and an optical waveguide 1 c provided on the substrate 5 . Light propagating through the optical waveguide 1 c is modulated by applying a modulation voltage to the modulation electrode. At least a part of the modulation electrode includes a base 2 a, 3 a formed on the substrate 5 and a projection part 2 b, 3 b having a width narrower than that of the base.

1. An optical modulator comprising:
 a substrate comprising an electro-optical material; 
 a plurality of modulation electrodes on the substrate; and 
 a plurality of optical waveguides on or in the substrate, wherein:
 light propagating through the plurality of optical waveguides is modulated when applying a modulation voltage on the plurality of modulation electrodes; 
 at least a part of each of the plurality of modulation electrodes comprises a base formed on the substrate and a projection part having a width narrower than that of the base; 
 
 each of the plurality of modulation electrodes comprises a pair of a signal electrode and a ground electrode; 
 a first gap is formed between the projection part of a first signal electrode and the projection part of a first ground electrode of a first modulation electrode; 
 a second gap is formed between the projection part of a second signal electrode and the projection part of a second ground electrode of a second modulation electrode; 
 a third gap is formed between the first modulation electrode and the second modulation electrode; and 
 first and second of the plurality of optical waveguides are disposed in the first gap and in the second gap, respectively, 
 wherein the second gap is wider than the first gap. 
 
     
     
       2. The optical modulator of  claim 1 , wherein the projection part is thicker than the base. 
     
     
       3. The optical modulator of  claim 1 , wherein the third gap is free of any optical waveguide. 
     
     
       4. The optical modulator of  claim 1 , wherein the difference between the widths of the plurality of the bases and the width of the plurality of corresponding projection parts is less than 30 μm. 
     
     
       5. The optical modulator  claim 1 , wherein the electro-optical material of the substrate is in direct contact with the base.